Non-real time measurements and background services are becoming more and more common in cellular communications networks. More and more information is being exchanged between the cellular communications network and wireless devices in the cellular communications network for various purposes, e.g., file sharing, measurements reporting for Minimization of Drive Tests (MDT), etc. Deploying radio nodes that provide a specific service or a restricted set of services becomes more justified in such wireless network architectures. Third Generation Partnership Project (3GPP) standards, however, provide limited possibilities for using such specialized service nodes, and in particular provide limited possibilities for specialized service nodes facilitating non-real time information collection throughout the cellular communications network. To enable full functionality, such specialized service nodes would have to, at a minimum, announce their presence and availability and, in one way or another, indicate the service(s) being provided by the specialized service node.
One example application of collecting non-real time measurements is MDT and enhanced MDT, which is being standardized for Universal Mobile Telecommunications System (UMTS) and Long Term Evolution (LTE). MDT is used as a means to compensate or partially replace costly drive tests an operator will otherwise have to perform by configuring a selection of User Equipment devices (UEs) in active or idle mode to do certain types of measurements, as specified in 3GPP Technical Report (TR) 36.805 (“Evolved Universal Terrestrial Radio Access (E-UTRA); Study on minimization of drive-tests in next generation networks”) and 3GPP TR 37.320 (“Radio measurement collection for Minimization of Drive Tests (MDT)”). The selection can be made based on International Mobile Subscriber Identity (IMSI), International Mobile Equipment Identity (IMEI), area, device capabilities, and any combinations thereof.
So far, the following use cases for MDT have been identified:                Coverage optimization,        Mobility optimization,        Capacity optimization,        Parameterization for common channels, and        Quality of Service (QoS) verification.        
Two modes of MDT exist, immediate MDT and logged MDT. Immediate MDT is the MDT functionality involving measurement performance by a UE in a high Radio Resource Control (RRC) activity state (e.g., RRC CONNECTED state in LTE, CELL_DCH state in Universal Terrestrial Radio Access (UTRA) Frequency Division Duplexing (FDD) and UTRA Time Division Duplexing (TDD), etc.) and reporting of the measurements to a network node (e.g., an Evolved Node B (eNB), a Radio Network Controller (RNC), a Node B (NB), a Base Station Controller (BSC), a Base Station (BS), a relay, etc.) available at the time of the occurrence of a reporting condition. Logged MDT is the MDT functionality involving measurement performance by a UE when operating in a low RRC activity state (e.g., RRC_IDLE in LTE and idle mode, CELL_PCH, URA_PCH or CELL_FACH states in UTRA FDD or UTRA TDD, etc.). The logging in a low activity state is carried out by the UE at points when configured conditions are satisfied. The measurement log is stored for reporting of measurements to a network node (e.g., eNB, Radio Network Controller (RNC) Node B (NB), BSC, BS, relay, etc.) at a later point in time.
One possible requirement for MDT in particular implementations is that the measurements in measurement logs and the reported measurements for immediate MDT are linked to available location information and/or other information or measurements that can be used to derive location information (e.g., Reference Signal Received Power (RSRP) measurements may be selected for this purpose in some implementations). The measurements in the measurement logs are also linked to a time stamp that is available in the UE.
In various implementations, the following measurements logs (or suitable alternatives) may be utilized:                Periodical downlink pilot measurements,        Serving cell becomes worse than threshold,        Transmit power headroom becomes less than threshold,        Random access failure,        Paging channel failure,        Broadcast channel failure, and        Radio link failure report.        
In addition to the information which may be specific for the type of the log, all of the measurement logs listed above include at least the following:                Location information when available (e.g., the location at which the concerned trigger and/or measurement took place),        Time information (e.g., the time at which the concerned trigger and/or measurement took place),        Cell identification (at least the serving cell is always included), and        Radio environment measurement (e.g., cell measurements that are available at the trigger for the logged measurement and/or average cell measurements during a certain period before/after the trigger for the logged measurement, where the cell measurements include RSRP and Reference Signal Received Quality (RSRQ) measurements).        
Signaling of MDT measurements and logs, including the associated location information, is via RRC signaling. For logged MDT, the configuration, measurement collection, and reporting of the concerned measurements will always be done in cells of the same Radio Access Technology (RAT) type. There is only one RAT-specific logged measurement configuration for logged MDT in the UE, and it is left up to the cellular communications network to retrieve any relevant data before providing a new configuration (e.g. for another RAT) since the previous log may be cleared.
When a logging area is configured, logged MDT measurements are performed as long as the UE is within this logging area. When the UE is not in the logging area or a Registered Public Land Mobile Network (PLMN) (RPLMN) of the UE is not part of an MDT PLMN list, logging is suspended, i.e. the logged measurement configuration and the log are kept (until a logging duration timer expires), but measurement results are not logged and the logging duration timer continues. In case a new PLMN that does not belong to the MDT PLMN list provides a logged measurement configuration, any previous logged measurement configuration and the corresponding log are cleared and overwritten without being retrieved by the cellular communications network.
Logged MDT measurements are configured with an MDT Measurement Configuration procedure, which is illustrated in FIG. 1. As shown, the cellular communications network, specifically the Radio Access Network (RAN) (i.e., the Universal Terrestrial Radio Access Network (UTRAN) or Evolved Universal Terrestrial Radio Access Network (E-UTRAN)), initiates the procedure to a UE in RRC Connected state by sending a LoggedMeasurementConfiguration message to the UE (step 100). The LoggedMeasurementConfiguration message is sent in the Downlink (DL) Dedicated Control Channel (DCCH) Message class, which is a set of RRC messages that may be sent from the E-UTRAN to the UE or from the E-UTRAN to the relay node on the DL DCCH logical channel. The LoggedMeasurementConfiguration message is used to transfer configuration parameters for logged MDT. A release operation for logged measurement configuration in the UE is realized only by replacing the logged measurement configuration with a new configuration (i.e., when the logged measurement configuration is overwritten) or by clearing the logged measurement configuration when a duration timer has expired or an expiration condition is met. The format of the LoggedMeasurementConfiguration message is illustrated in FIG. 2.
At the UE, upon receiving the LoggedMeasurementConfiguration message, the UE starts a timer T330 with the timer value set to a LoggingDuration specified in the LoggedMeasurementConfiguration message. Upon expiry of the timer T330 or when memory reserved for the logged measurement information becomes full (which triggers T330 expiry), the UE is allowed to discard VarLogMeasConfig. VarLogMeasConfig is defined in 3GPP Technical Specification (TS) 36.331 as the UE variable that includes the configuration of the logging of measurements to be performed by the UE while in RRC_IDLE, covering intra-frequency, inter-frequency, and inter-RAT mobility related measurements. The variable VarLogMeasConfig is signaled to the UE by the network node in an RRC message. Forty-eight (48) hours after expiry of the timer T330, the UE is also allowed to discard the stored logged measurements and VarLogMeasReport. VarLogMeasReport is also defined in 3GPP TS 36.331 as the UE variable that includes the logged measurements information. The UE variable VarLogMeasReport is also signaled to the UE by the network node in an RRC message.
Within the LoggedMeasurementConfiguration message,
LoggingDuration defines an amount of time that measurements are to be logged after the UE receives the LoggedMeasurementConfiguration message. LoggingDuration is one of the predefined values in the range of 10 minutes to 120 minutes. LoggingInterval is an interval of measurement logging and is one of the predefined values in the range of 1.28 seconds to 2.56 seconds. The Trace Collection Entity (TCE) Identifier (ID), tce-Id, denotes a particular TCE. The UE returns the tce-Id to the cellular communications network together with the logged data. The cellular communications network has a configured mapping of an Internet Protocol (IP) address of the TCE (to which corresponding trace records are transferred) and the TCE ID. The mapping needs to be unique within the PLMN.
If areaConfiguration is configured, the UE will log measurements as long as the UE is within the configured logging area. The scope of the logging area may consist of one of a list of 32 global cell identities. If this list is configured, the UE will only log measurements when camping in any of these cells. Alternatively, the logging area may consist of a list of eight Tracking Areas (TAs), eight Local Areas (LAs), or eight Registered Areas (RAs). If this list is configured, the UE will only log measurements when camping in any cell belonging to the preconfigured TA/LA/RAs. If no logging area is configured, the logged measurement configuration is valid in the entire MDT PLMN of the UE, i.e. the UE will log measurements throughout the MDT PLMN.
FIG. 3 illustrates an example of logged MDT reporting as described in 3GPP TS 32.421, “Telecommunication management; Subscriber and equipment trace; Trace concepts and requirements,” V11.4.0, September 2012 and 3GPP TS 32.422, “Telecommunication management; Subscriber and equipment trace; Trace control and configuration management,” V11.5.0, September 2012, both of which are incorporated herein by reference herein their entireties. In case of logged MDT, the UE collects the measurements while it is in IDLE mode. As illustrated, MDT is configured as discussed above (step 200). The UE enters the IDLE mode (step 202). While in the IDLE mode, the UE performs MDT measurement logging (step 204). Sometime after measurement logging is complete (i.e., after the logging duration has expired), the UE enters the RRC CONNECTED mode (step 206), and the UE indicates MDT log availability in an RRCConnectionSetupComplete message sent to the RNC/eNB (step 208). The UE will not indicate MDT log availability in another RAT or in another RPLMN.
When the RNC/eNB receives the indication of the MDT log availability, the RNC/eNB can request the MDT log (if the UE is still in the same RAT type where the MDT configuration was done) by sending a UEInformationRequest message to the UE (step 210). The MDT log is then sent to the RNC/eNB in a UEInformationResponse message (step 212). The reporting may occur in different cells than which the logged measurement configuration is signaled. At the reception of the UEInformationResponse message, the RNC/eNB saves the received MDT log to a trace record (step 214) and sends the trace record to the corresponding TCE (step 216).
The reported MDT log consists of measurement results for the serving cell of the UE (the measurement quantity), available UE measurements performed in IDLE mode for intra-frequency/inter-frequency/inter-RAT, time stamps, and location information. The number of neighboring cells to be logged is limited by a fixed upper limit per frequency for each category (e.g., six for intra-frequency neighboring cells, three for inter-frequency neighboring cells, etc.). The measurement reports for neighboring cells (which are part of the same MDT log/report as the measurements for the serving cell but contained in different Information Elements (IEs)) consist of: Physical Cell Identity (PCI) of the logged cell, carrier frequency, RSRP and RSRQ for E-UTRA, Received Signal Code Power (RSCP) and Energy per Chip (Ec)/Noise Spectral Density (No) for UTRA, Primary Common Control Physical Channel (P-CCPCH) RSCP for UTRA 1.28 TDD, Received Signal Level (Rxlev) for Global System for Mobile Communications Edge Radio Access Network (GERAN), and Pilot Pseudo noise (Pn) Phase and Pilot Strength for Code Division Multiple Access (CDMA) 2000.
In case of immediate MDT, as illustrated in FIG. 4, the MDT is first configured as discussed above (step 300). For immediate MDT, the UE is in RRC CONNECTED mode. The UE periodically logs MDT measurements and reports the logged MDT measurements to the RNC/eNB via RRC signaling (as part of existing RRC measurements) where the logged MDT measurements are stored to a trace record (steps 302 through 312). The immediate MDT measurement reports are periodic (with intervals in the range of 120 milliseconds (ms) to 1 hour) or event-triggered. The trace records are sent to the TCE via an Element Manager (EM), where the EM can reside in the RNC/eNB (steps 314 and 316).
In addition to MDT logs, the UE logs failed RRC connection establishments for LTE and UMTS, i.e. a log is created when the RRC connection establishment procedure fails. For LTE, the trigger for creating a log related to a failed RRC connection establishment is when timer T300 expires. For UMTS, the trigger for creating a log related to a failed RRC connection establishment is when V300 is greater than N300. Unlike logged MDT and immediate MDT, the UE logs failed RRC connection establishments without the need for prior configuration by the cellular communications network.
For an RRC connection establishment failure log, the UE stores the selected PLMN on the RRC connection establishment failure. The UE may report the RRC connection establishment failure log only if that PLMN is the same as the RPLMN. The RRC connection establishment failure log includes:                Time stamp, which is the elapsed time between logging and reporting the log,        The global cell identity of the serving cell when the RRC connection establishment fails, i.e. the cell which the UE attempted to access,        The latest available radio measurements for any frequency or RAT,        The latest detailed location information, if available,        For LTE:                    Number of random access preambles transmitted,            Indication whether the maximum transmission power was used, and            Contention detected,                        For UMTS FDD:                    Number of RRC Connection Request attempts (e.g., T300 expiry after receiving an Acknowledgement (ACK) and an Acquisition Indicator Channel (AICH)),            Indication of probable contention, e.g. mismatch of UE identity in RRC CONNECTION SETUP message, and                        For UMTS TDD:                    Number of RRC connection request attempts,            Indication of probable contention, e.g. mismatch of UE identity in RRC CONNECTION SETUP message,            Whether the Fast Physical Access Channel (FPACH) is received or whether the maximum number Mmax of synchronization attempts is reached, and            Failure indication of the Enhanced Dedicated Channel Random Access Uplink Control Channel (E-RUCCH) transmission. The failure indication is only applied if common Enhanced Dedicated Channel (E-DCH) is supported by the UE and the cellular communications network.                        
With regard to RRC connection establishment failure logging in LTE, the content of the report is illustrated in FIG. 5. The information for the RRC connection establishment failure log is logged at expiry of timer T300, which is initiated when the UE sends an RRCConnectionRequest. The timer T300 is stopped when the UE receives an RRCConnectionSetup or RRCConnectionReject message, when there is cell re-selection, or upon abortion of connection establishment by upper layers. The timer T300 is defined in 3GPP TS 36.331 as follows:
TimerStartStopAt expiryT300Transmission ofReception ofPerform theRRCConnectionRequestRRCConnectionSetupactions asorspecified inRRCConnectionReject5.3.3.6message, cell re-selection, and uponabortion of connectionestablishment by upperlayers
The availability of the RRC connection establishment failure report (the connEstFailInfoAvailable indication) may be indicated upon reception by the UE of the following messages:                RRCConnectionSetup,        RRCConnectionReconfiguration including the mobilityControlInfo (handover), and        RRCConnectionReestablishment.        
The time stamping for the RRC connection establishment failure report is upon receiving a UEInformationRequest message when the report is available. The UEInformationRequest message may be sent to the UE when the availability of the report (by the indicator connEstFailInfoAvailable) has been indicated by the UE. The UE then includes the available report in a UEInformationResponse message. Specifically, upon receiving the UEInformationRequest message, the UE will:                If connEstFail-ReportReq is set to true and the UE has connection establishment failure information in VarConnEstFail-Report and if the RPLMN is equal to plmn-Identity stored in VarConnEstFail-Report:                    Set timeSinceFailure in VarConnEstFail-Report to the time that elapsed since the last connection establishment failure; and            Set the connEstFail-Report in the UEInformationResponse message to the value of connEstFail-Report in VarConnEstFail-Report.                        
In UTRA, the logging of an RRC connection establishment failure depends on timer V300. Namely, when V300 is greater than N300, the UE performs the following actions for logging of a failed RRC connection establishment (as specified in 3GPP TS 25.311, section 8.1.3.11):                If the RRC connection establishment fails, the UE shall perform logging of information for later retrieval. The UE shall store connection establishment failure information in the variable LOGGED_CONNECTION_ESTABLISHMENT_FAILURE by setting its respective fields to corresponding values.        
From the above, it becomes evident that there is a substantial difference between time stamping for RRC connection establishment failure log reporting and time stamping for MDT measurement logs in RRC IDLE mode. This difference is schematically illustrated in FIG. 6. As shown, the major difference is that the time stamp for the RRC connection establishment failure log my occur after up to 48 hours after a reference time (failure logged), while the maximum time for maximum time for the logged MDT measurements to be logged and time-stamped is two hours with respect to a reference time (MDT configuration received).
Current MDT logging and reporting mechanisms as well as current RRC connection establishment failure logging and reporting mechanisms have a number of problems. As such, there is a need for systems and methods for enhanced MDT logging and/or reporting as well as enhanced RRC connection establishment failure logging and/or reporting.